You will end up with xxRRRIxxxx, where R are re-encoded frames. Smart copy will re-encode the part that losts its reference images with a fixed quantizer. Why broken ? Because they lost their reference frames. It means that if you have a stream like this : xxAxxIxxBxxxIxxx, and remove [A,B[, you will end up with xxOOOIxxxxx, with OOO being broken frames. These frames are Intra frame, also called I-Frame or KeyFrame.

From time to time a complete frame is encoded with no temporal reference to other frames. Most video codec use the previous frame as reference and only encode the delta. In process mode, avidemux internals ensure everything is allright. This paragraph only applies when video is in copy mode. Said otherwise, be sure to cut a stream which always contains the audio. When removing parts, the audio inside the stream will keep sync, not an external audio. You can remove as much as you want from the video stream. It can be used, for example, to remove commercials from a video capture. The Markers->Delete menu entry will remove [A,B[ from the stream. If you set markers video will be saved from A to B including B. Markers position is also recalled at the bottom of the screen. You can also jump to A or B marker using Markers->Go to A or Markers->Go to B menu entries.

A and B markers are used to set the start and end of a sequence.

Avidemux cut